From 93ef1429e556f739a208e3968883ed51480580e8 Mon Sep 17 00:00:00 2001 From: Qais Yousef Date: Mon, 23 Mar 2020 13:50:54 +0000 Subject: cpu/hotplug: Add new {add,remove}_cpu() functions The new functions use device_{online,offline}() which are userspace safe. This is in preparation to move cpu_{up, down} kernel users to use a safer interface that is not racy with userspace. Suggested-by: "Paul E. McKenney" Signed-off-by: Qais Yousef Signed-off-by: Thomas Gleixner Reviewed-by: Paul E. McKenney Link: https://lkml.kernel.org/r/20200323135110.30522-2-qais.yousef@arm.com --- include/linux/cpu.h | 2 ++ 1 file changed, 2 insertions(+) (limited to 'include') diff --git a/include/linux/cpu.h b/include/linux/cpu.h index 1ca2baf817ed..cf8cf38dca43 100644 --- a/include/linux/cpu.h +++ b/include/linux/cpu.h @@ -89,6 +89,7 @@ extern ssize_t arch_cpu_release(const char *, size_t); #ifdef CONFIG_SMP extern bool cpuhp_tasks_frozen; int cpu_up(unsigned int cpu); +int add_cpu(unsigned int cpu); void notify_cpu_starting(unsigned int cpu); extern void cpu_maps_update_begin(void); extern void cpu_maps_update_done(void); @@ -118,6 +119,7 @@ extern void cpu_hotplug_disable(void); extern void cpu_hotplug_enable(void); void clear_tasks_mm_cpumask(int cpu); int cpu_down(unsigned int cpu); +int remove_cpu(unsigned int cpu); #else /* CONFIG_HOTPLUG_CPU */ -- cgit v1.2.3-70-g09d2 From 0441a5597c5d02ed7abed1d989eaaa1595dedac5 Mon Sep 17 00:00:00 2001 From: Qais Yousef Date: Mon, 23 Mar 2020 13:50:55 +0000 Subject: cpu/hotplug: Create a new function to shutdown nonboot cpus This function will be used later in machine_shutdown() for some architectures. disable_nonboot_cpus() is not safe to use when doing machine_down(), because it relies on freeze_secondary_cpus() which in turn is a suspend/resume related freeze and could abort if the logic detects any pending activities that can prevent finishing the offlining process. Signed-off-by: Qais Yousef Signed-off-by: Thomas Gleixner Link: https://lkml.kernel.org/r/20200323135110.30522-3-qais.yousef@arm.com --- include/linux/cpu.h | 2 ++ kernel/cpu.c | 42 ++++++++++++++++++++++++++++++++++++++++++ 2 files changed, 44 insertions(+) (limited to 'include') diff --git a/include/linux/cpu.h b/include/linux/cpu.h index cf8cf38dca43..64a246e9c8db 100644 --- a/include/linux/cpu.h +++ b/include/linux/cpu.h @@ -120,6 +120,7 @@ extern void cpu_hotplug_enable(void); void clear_tasks_mm_cpumask(int cpu); int cpu_down(unsigned int cpu); int remove_cpu(unsigned int cpu); +extern void smp_shutdown_nonboot_cpus(unsigned int primary_cpu); #else /* CONFIG_HOTPLUG_CPU */ @@ -131,6 +132,7 @@ static inline int cpus_read_trylock(void) { return true; } static inline void lockdep_assert_cpus_held(void) { } static inline void cpu_hotplug_disable(void) { } static inline void cpu_hotplug_enable(void) { } +static inline void smp_shutdown_nonboot_cpus(unsigned int primary_cpu) { } #endif /* !CONFIG_HOTPLUG_CPU */ /* Wrappers which go away once all code is converted */ diff --git a/kernel/cpu.c b/kernel/cpu.c index 069802f7010f..03c727195b65 100644 --- a/kernel/cpu.c +++ b/kernel/cpu.c @@ -1069,6 +1069,48 @@ int remove_cpu(unsigned int cpu) } EXPORT_SYMBOL_GPL(remove_cpu); +void smp_shutdown_nonboot_cpus(unsigned int primary_cpu) +{ + unsigned int cpu; + int error; + + cpu_maps_update_begin(); + + /* + * Make certain the cpu I'm about to reboot on is online. + * + * This is inline to what migrate_to_reboot_cpu() already do. + */ + if (!cpu_online(primary_cpu)) + primary_cpu = cpumask_first(cpu_online_mask); + + for_each_online_cpu(cpu) { + if (cpu == primary_cpu) + continue; + + error = cpu_down_maps_locked(cpu, CPUHP_OFFLINE); + if (error) { + pr_err("Failed to offline CPU%d - error=%d", + cpu, error); + break; + } + } + + /* + * Ensure all but the reboot CPU are offline. + */ + BUG_ON(num_online_cpus() > 1); + + /* + * Make sure the CPUs won't be enabled by someone else after this + * point. Kexec will reboot to a new kernel shortly resetting + * everything along the way. + */ + cpu_hotplug_disabled++; + + cpu_maps_update_done(); +} + #else #define takedown_cpu NULL #endif /*CONFIG_HOTPLUG_CPU*/ -- cgit v1.2.3-70-g09d2 From d720f98604391dab6aa3cb4c1bc005ed1aba4703 Mon Sep 17 00:00:00 2001 From: Qais Yousef Date: Mon, 23 Mar 2020 13:51:01 +0000 Subject: cpu/hotplug: Provide bringup_hibernate_cpu() arm64 uses cpu_up() in the resume from hibernation code to ensure that the CPU on which the system hibernated is online. Provide a core function for this. [ tglx: Split out from the combo arm64 patch ] Signed-off-by: Qais Yousef Signed-off-by: Thomas Gleixner Acked-by: Catalin Marinas Cc: Will Deacon Link: https://lkml.kernel.org/r/20200323135110.30522-9-qais.yousef@arm.com --- include/linux/cpu.h | 1 + kernel/cpu.c | 23 +++++++++++++++++++++++ 2 files changed, 24 insertions(+) (limited to 'include') diff --git a/include/linux/cpu.h b/include/linux/cpu.h index 64a246e9c8db..9dc1e892e193 100644 --- a/include/linux/cpu.h +++ b/include/linux/cpu.h @@ -93,6 +93,7 @@ int add_cpu(unsigned int cpu); void notify_cpu_starting(unsigned int cpu); extern void cpu_maps_update_begin(void); extern void cpu_maps_update_done(void); +int bringup_hibernate_cpu(unsigned int sleep_cpu); #else /* CONFIG_SMP */ #define cpuhp_tasks_frozen 0 diff --git a/kernel/cpu.c b/kernel/cpu.c index 03c727195b65..f803678684e9 100644 --- a/kernel/cpu.c +++ b/kernel/cpu.c @@ -1275,6 +1275,29 @@ int add_cpu(unsigned int cpu) } EXPORT_SYMBOL_GPL(add_cpu); +/** + * bringup_hibernate_cpu - Bring up the CPU that we hibernated on + * @sleep_cpu: The cpu we hibernated on and should be brought up. + * + * On some architectures like arm64, we can hibernate on any CPU, but on + * wake up the CPU we hibernated on might be offline as a side effect of + * using maxcpus= for example. + */ +int bringup_hibernate_cpu(unsigned int sleep_cpu) +{ + int ret; + + if (!cpu_online(sleep_cpu)) { + pr_info("Hibernated on a CPU that is offline! Bringing CPU up.\n"); + ret = cpu_up(sleep_cpu); + if (ret) { + pr_err("Failed to bring hibernate-CPU up!\n"); + return ret; + } + } + return 0; +} + #ifdef CONFIG_PM_SLEEP_SMP static cpumask_var_t frozen_cpus; -- cgit v1.2.3-70-g09d2 From b99a26593b5190fac6b5c1f81a7f8cc128a25c98 Mon Sep 17 00:00:00 2001 From: Qais Yousef Date: Mon, 23 Mar 2020 13:51:09 +0000 Subject: cpu/hotplug: Move bringup of secondary CPUs out of smp_init() This is the last direct user of cpu_up() before it can become an internal implementation detail of the cpu subsystem. Signed-off-by: Qais Yousef Signed-off-by: Thomas Gleixner Link: https://lkml.kernel.org/r/20200323135110.30522-17-qais.yousef@arm.com --- include/linux/cpu.h | 1 + kernel/cpu.c | 12 ++++++++++++ kernel/smp.c | 9 +-------- 3 files changed, 14 insertions(+), 8 deletions(-) (limited to 'include') diff --git a/include/linux/cpu.h b/include/linux/cpu.h index 9dc1e892e193..8b295f78da25 100644 --- a/include/linux/cpu.h +++ b/include/linux/cpu.h @@ -94,6 +94,7 @@ void notify_cpu_starting(unsigned int cpu); extern void cpu_maps_update_begin(void); extern void cpu_maps_update_done(void); int bringup_hibernate_cpu(unsigned int sleep_cpu); +void bringup_nonboot_cpus(unsigned int setup_max_cpus); #else /* CONFIG_SMP */ #define cpuhp_tasks_frozen 0 diff --git a/kernel/cpu.c b/kernel/cpu.c index f803678684e9..4783d811ccf8 100644 --- a/kernel/cpu.c +++ b/kernel/cpu.c @@ -1298,6 +1298,18 @@ int bringup_hibernate_cpu(unsigned int sleep_cpu) return 0; } +void bringup_nonboot_cpus(unsigned int setup_max_cpus) +{ + unsigned int cpu; + + for_each_present_cpu(cpu) { + if (num_online_cpus() >= setup_max_cpus) + break; + if (!cpu_online(cpu)) + cpu_up(cpu); + } +} + #ifdef CONFIG_PM_SLEEP_SMP static cpumask_var_t frozen_cpus; diff --git a/kernel/smp.c b/kernel/smp.c index 97f1d9765c94..786092aabdcd 100644 --- a/kernel/smp.c +++ b/kernel/smp.c @@ -597,20 +597,13 @@ void __init setup_nr_cpu_ids(void) void __init smp_init(void) { int num_nodes, num_cpus; - unsigned int cpu; idle_threads_init(); cpuhp_threads_init(); pr_info("Bringing up secondary CPUs ...\n"); - /* FIXME: This should be done in userspace --RR */ - for_each_present_cpu(cpu) { - if (num_online_cpus() >= setup_max_cpus) - break; - if (!cpu_online(cpu)) - cpu_up(cpu); - } + bringup_nonboot_cpus(setup_max_cpus); num_nodes = num_online_nodes(); num_cpus = num_online_cpus(); -- cgit v1.2.3-70-g09d2 From 33c3736ec88811b9b6f6ce2cc8967f6b97c3db5e Mon Sep 17 00:00:00 2001 From: Qais Yousef Date: Mon, 23 Mar 2020 13:51:10 +0000 Subject: cpu/hotplug: Hide cpu_up/down() Use separate functions for the device core to bring a CPU up and down. Users outside the device core must use add/remove_cpu() which will take care of extra housekeeping work like keeping sysfs in sync. Make cpu_up/down() static and replace the extra layer of indirection. [ tglx: Removed the extra wrapper functions and adjusted function names ] Signed-off-by: Qais Yousef Signed-off-by: Thomas Gleixner Link: https://lkml.kernel.org/r/20200323135110.30522-18-qais.yousef@arm.com --- drivers/base/cpu.c | 4 ++-- include/linux/cpu.h | 4 ++-- kernel/cpu.c | 42 ++++++++++++++++++++++++++++-------------- 3 files changed, 32 insertions(+), 18 deletions(-) (limited to 'include') diff --git a/drivers/base/cpu.c b/drivers/base/cpu.c index 6265871a4af2..b93a8f82f215 100644 --- a/drivers/base/cpu.c +++ b/drivers/base/cpu.c @@ -55,7 +55,7 @@ static int cpu_subsys_online(struct device *dev) if (from_nid == NUMA_NO_NODE) return -ENODEV; - ret = cpu_up(cpuid); + ret = cpu_device_up(dev); /* * When hot adding memory to memoryless node and enabling a cpu * on the node, node number of the cpu may internally change. @@ -69,7 +69,7 @@ static int cpu_subsys_online(struct device *dev) static int cpu_subsys_offline(struct device *dev) { - return cpu_down(dev->id); + return cpu_device_down(dev); } void unregister_cpu(struct cpu *cpu) diff --git a/include/linux/cpu.h b/include/linux/cpu.h index 8b295f78da25..9ead281157d3 100644 --- a/include/linux/cpu.h +++ b/include/linux/cpu.h @@ -88,8 +88,8 @@ extern ssize_t arch_cpu_release(const char *, size_t); #ifdef CONFIG_SMP extern bool cpuhp_tasks_frozen; -int cpu_up(unsigned int cpu); int add_cpu(unsigned int cpu); +int cpu_device_up(struct device *dev); void notify_cpu_starting(unsigned int cpu); extern void cpu_maps_update_begin(void); extern void cpu_maps_update_done(void); @@ -120,8 +120,8 @@ extern void lockdep_assert_cpus_held(void); extern void cpu_hotplug_disable(void); extern void cpu_hotplug_enable(void); void clear_tasks_mm_cpumask(int cpu); -int cpu_down(unsigned int cpu); int remove_cpu(unsigned int cpu); +int cpu_device_down(struct device *dev); extern void smp_shutdown_nonboot_cpus(unsigned int primary_cpu); #else /* CONFIG_HOTPLUG_CPU */ diff --git a/kernel/cpu.c b/kernel/cpu.c index 4783d811ccf8..30848496cbc7 100644 --- a/kernel/cpu.c +++ b/kernel/cpu.c @@ -1041,7 +1041,7 @@ static int cpu_down_maps_locked(unsigned int cpu, enum cpuhp_state target) return _cpu_down(cpu, 0, target); } -static int do_cpu_down(unsigned int cpu, enum cpuhp_state target) +static int cpu_down(unsigned int cpu, enum cpuhp_state target) { int err; @@ -1051,11 +1051,18 @@ static int do_cpu_down(unsigned int cpu, enum cpuhp_state target) return err; } -int cpu_down(unsigned int cpu) +/** + * cpu_device_down - Bring down a cpu device + * @dev: Pointer to the cpu device to offline + * + * This function is meant to be used by device core cpu subsystem only. + * + * Other subsystems should use remove_cpu() instead. + */ +int cpu_device_down(struct device *dev) { - return do_cpu_down(cpu, CPUHP_OFFLINE); + return cpu_down(dev->id, CPUHP_OFFLINE); } -EXPORT_SYMBOL(cpu_down); int remove_cpu(unsigned int cpu) { @@ -1178,8 +1185,8 @@ static int _cpu_up(unsigned int cpu, int tasks_frozen, enum cpuhp_state target) } /* - * The caller of do_cpu_up might have raced with another - * caller. Ignore it for now. + * The caller of cpu_up() might have raced with another + * caller. Nothing to do. */ if (st->state >= target) goto out; @@ -1223,7 +1230,7 @@ out: return ret; } -static int do_cpu_up(unsigned int cpu, enum cpuhp_state target) +static int cpu_up(unsigned int cpu, enum cpuhp_state target) { int err = 0; @@ -1257,11 +1264,18 @@ out: return err; } -int cpu_up(unsigned int cpu) +/** + * cpu_device_up - Bring up a cpu device + * @dev: Pointer to the cpu device to online + * + * This function is meant to be used by device core cpu subsystem only. + * + * Other subsystems should use add_cpu() instead. + */ +int cpu_device_up(struct device *dev) { - return do_cpu_up(cpu, CPUHP_ONLINE); + return cpu_up(dev->id, CPUHP_ONLINE); } -EXPORT_SYMBOL_GPL(cpu_up); int add_cpu(unsigned int cpu) { @@ -1289,7 +1303,7 @@ int bringup_hibernate_cpu(unsigned int sleep_cpu) if (!cpu_online(sleep_cpu)) { pr_info("Hibernated on a CPU that is offline! Bringing CPU up.\n"); - ret = cpu_up(sleep_cpu); + ret = cpu_up(sleep_cpu, CPUHP_ONLINE); if (ret) { pr_err("Failed to bring hibernate-CPU up!\n"); return ret; @@ -1306,7 +1320,7 @@ void bringup_nonboot_cpus(unsigned int setup_max_cpus) if (num_online_cpus() >= setup_max_cpus) break; if (!cpu_online(cpu)) - cpu_up(cpu); + cpu_up(cpu, CPUHP_ONLINE); } } @@ -2129,9 +2143,9 @@ static ssize_t write_cpuhp_target(struct device *dev, goto out; if (st->state < target) - ret = do_cpu_up(dev->id, target); + ret = cpu_up(dev->id, target); else - ret = do_cpu_down(dev->id, target); + ret = cpu_down(dev->id, target); out: unlock_device_hotplug(); return ret ? ret : count; -- cgit v1.2.3-70-g09d2 From e98eac6ff1b45e4e73f2e6031b37c256ccb5d36b Mon Sep 17 00:00:00 2001 From: Thomas Gleixner Date: Fri, 27 Mar 2020 12:06:44 +0100 Subject: cpu/hotplug: Ignore pm_wakeup_pending() for disable_nonboot_cpus() A recent change to freeze_secondary_cpus() which added an early abort if a wakeup is pending missed the fact that the function is also invoked for shutdown, reboot and kexec via disable_nonboot_cpus(). In case of disable_nonboot_cpus() the wakeup event needs to be ignored as the purpose is to terminate the currently running kernel. Add a 'suspend' argument which is only set when the freeze is in context of a suspend operation. If not set then an eventually pending wakeup event is ignored. Fixes: a66d955e910a ("cpu/hotplug: Abort disabling secondary CPUs if wakeup is pending") Reported-by: Boqun Feng Signed-off-by: Thomas Gleixner Cc: Pavankumar Kondeti Cc: stable@vger.kernel.org Link: https://lkml.kernel.org/r/874kuaxdiz.fsf@nanos.tec.linutronix.de --- include/linux/cpu.h | 12 +++++++++--- kernel/cpu.c | 4 ++-- 2 files changed, 11 insertions(+), 5 deletions(-) (limited to 'include') diff --git a/include/linux/cpu.h b/include/linux/cpu.h index 9ead281157d3..beaed2dc269e 100644 --- a/include/linux/cpu.h +++ b/include/linux/cpu.h @@ -144,12 +144,18 @@ static inline void get_online_cpus(void) { cpus_read_lock(); } static inline void put_online_cpus(void) { cpus_read_unlock(); } #ifdef CONFIG_PM_SLEEP_SMP -extern int freeze_secondary_cpus(int primary); +int __freeze_secondary_cpus(int primary, bool suspend); +static inline int freeze_secondary_cpus(int primary) +{ + return __freeze_secondary_cpus(primary, true); +} + static inline int disable_nonboot_cpus(void) { - return freeze_secondary_cpus(0); + return __freeze_secondary_cpus(0, false); } -extern void enable_nonboot_cpus(void); + +void enable_nonboot_cpus(void); static inline int suspend_disable_secondary_cpus(void) { diff --git a/kernel/cpu.c b/kernel/cpu.c index 30848496cbc7..12ae636e9cb6 100644 --- a/kernel/cpu.c +++ b/kernel/cpu.c @@ -1327,7 +1327,7 @@ void bringup_nonboot_cpus(unsigned int setup_max_cpus) #ifdef CONFIG_PM_SLEEP_SMP static cpumask_var_t frozen_cpus; -int freeze_secondary_cpus(int primary) +int __freeze_secondary_cpus(int primary, bool suspend) { int cpu, error = 0; @@ -1352,7 +1352,7 @@ int freeze_secondary_cpus(int primary) if (cpu == primary) continue; - if (pm_wakeup_pending()) { + if (suspend && pm_wakeup_pending()) { pr_info("Wakeup pending. Abort CPU freeze\n"); error = -EBUSY; break; -- cgit v1.2.3-70-g09d2